Towels (you'll get wet, too, haha)
Sunscreen!
Chairs
Canopy (or if they have covered parking, I just crate out of my car and open the back hatch and set up chairs around that)
4ft leash (DD rule)
Multiple toys to throw (I always brought balls, but this year I'm going to try out a bumper)
Food/water bowls (we're usually there all day)
First aid kit
Extra leashes
Crate fan (so I could walk away from the car under the covered parking)
Packed cooler with waters, etc. Vending was always horrible at the one place we usually compete.

That's all I can think of right now. Will add more if I remember something.

LOL I only bring like one towel to most events unless it's supposed to be chilly! Other than that Lizmo's list is pretty complete! And only bring a camera/video cam if you have someone to use it for you - you'll likely be busy and have your hands full most of the time and you obvs don't want to have it on the dock.

Dekka gets cold if the water is less than 85. But they are all for me. I hate being wet, unless I am swimming or showering. So one towel or so after every wave.

Oh even my dogs were cold at nationals last year. Jumping in the stormy weather during November (or was it October?), yikes! Thankfully we brought jackets for the dogs but during summer we let the dog air dry.